Advocates of programs that select ''bright'' students for advanced schooling say these children need special classes to keep them motivated, or they would get bored, disruptive, and even drop out. But in Miami, skin color and income, not creativity or intelligence, appear to be the deciding factors for participation in gifted programs, says a new study.

In Dade County, the largest school district in Florida, white students are 360 percent more likely to be chosen for gifted programs than are black and Hispanic children, according to research conducted by the Miami consulting firm Mason-Dixon Political/Media Research and published in the September issue of Florida Trend magazine.

In some Miami schools, nearly half of all white children from middle-income households are classified as ''gifted.''

No one suggests that Miami really has 10 times as many ''gifted'' white fifth-graders as the national average. What's happening, say critics, is that in Florida and across the South, school administrators are channeling large numbers of students into these classes, in part to placate parents who are demanding better-quality education for their children.

The number of students admitted into gifted programs in Florida has jumped 42 percent in the past five years. During the same period, student enrollment in the public-school system went up only 18 percent.

There is an economic incentive for fattening the gifted rolls. Under Florida funding formulas, school districts on average qualify for an extra $700 or more for every student classified as gifted.

But Florida's practices are not unusual. The Georgia public-school system came under pressure last December following an Atlanta Journal-Constitution investigation, which showed that since desegregation in the 1970s, teachers have routinely shifted white children into gifted programs while ignoring blacks and Hispanics.

In recent years, Dade County has reworked its selection process, incorporating tests designed to reflect the cultural background of students. Children may also be chosen based on the recommendation of a private psychologist. The $300 cost is considered a worthwhile investment by many parents. Such changes have increased the number of black and Hispanic students in Miami's gifted program. But the number of affluent white children has also risen.

The director of Dade County Gifted Programs, Jill McCauley, says the selection process has flaws in it, however, ''if we wait to have a better plan we'd never get started.'' A middle-class parent, white or black, she says, ''is much more aware of what's available and pursues it more aggressively.''

Indeed, figures show that black children from middle-class homes get into the program in larger numbers than white children from a low-income homes.

The University of Miami is now designing new tests for Cubans, Haitians, and African-Americans. The aim is to include more gifted children from low-income families whose parents don't push to have them in the program.

Still, critics say, labeling children gifted reinforces damaging racial and economic stereotypes. The money spent on gifted students should be spent on improving education for all children, they say.

White students are 360 percent more likely to be chosen for gifted programs than black and Hispanic children.